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Abstract
The objective of this study was to assess if the setting expansion, compressive strength, compressive modulus and Knoop hardness is reduced in Type III, IV and V gypsum products when excess water is added to recommended water/powder (W/P) ratios for full-arch implant master casts. Four properties were measured: linear setting expansion, compressive strength, compressive modulus, and Knoop hardness. Three dental stones were evaluated: ISO Type III, Type IV, and Type V. Water was added to recommended W/P ratios as follows: (1) 0%, the manufacturer’s recommend W/P ratio, (2) 50%, 1.5 times the manufacturer’s recommendation of water, (3) 100%, three times the manufacturer’s recommendation of water, (4) 150%, 2.5 times the manufacturer’s recommendation of water, and (5) 200%, three times the manufacturer’s recommendation of water. For all three gypsum types, 50% water additions minimally affected the setting expansion and compressive modulus (p > 0.05), but lowered compressive strength by 26% to 52% (p < 0.05). Knoop hardness was lowered by 24% and 48% for Types V and III (p < 0.05), whereas Type IV was not significantly affected (p > 0.05). With few exceptions, the physical properties for the three gypsum types reached minimum values at 100% dilution, with few changes noted at higher dilutions. Increased W/P ratios did not adequately reduce the setting expansion and adversely affected other physical properties. Of the gypsums tested, Type IV is still recommended due to its lower setting expansion for full-arch implant master casts.
Highlights
Osseointegrated dental implants have been shown to have a high success rate through multiple studies [1,2,3,4,5,6,7], the criteria used to evaluate success, survival and failure has not always been delineated throughout the dental literature [8,9]
Due to the necessity of accuracy and dimensional stability, Type IV dental stone is typically used for implant master casts planned for multiple implant-supported complete dental prostheses [10]
The setting expansion and strength of dental stone are properties of concern when fabricating master casts for implant-supported complete dentures
Summary
Osseointegrated dental implants have been shown to have a high success rate through multiple studies [1,2,3,4,5,6,7], the criteria used to evaluate success, survival and failure has not always been delineated throughout the dental literature [8,9]. Several studies have looked at fit and improving the accuracy of implant master casts, including using low-fusing alloys [10,12], various gypsum types, [10] the use of different die systems [13], the fabrication of casts from different available materials including resin-containing and epoxy materials [14] and dental plaster [15]. Due to the necessity of accuracy and dimensional stability, Type IV dental stone is typically used for implant master casts planned for multiple implant-supported complete dental prostheses [10]. The setting expansion and strength of dental stone are properties of concern when fabricating master casts for implant-supported complete dentures. For an implant-supported complete denture, the most important aspect of success is the accuracy of the implant analog position; minimizing setting expansion is critical to achieving clinical success
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